How Costa Rica’s Reventazón Hydroelectric Project uses a river offset to protect biodiversity
The Reventazón Hydroelectric Project won the IHA Blue Planet Prize in 2019 for its approaches to biodiversity conservation
Costa Rica is home to some of Central America’s most important ecosystems, where rich biodiversity coexists with growing demands for renewable energy. In this landscape, the Reventazón Hydroelectric Project stands out – not just as the country’s largest hydropower facility, but as one of the first in Latin America to implement a river offset approach. Through strategic basin planning, the project has enabled the development of low-carbon energy while delivering lasting benefits for biodiversity conservation, writes Alex Trembath.
With an installed capacity of more than 300MW, Reventazón is the largest hydropower facility in Central America and a major contributor to Costa Rica’s renewable energy mix. But its value to the region extends beyond energy. Through early planning, strong partnerships and a pioneering biodiversity strategy, the project demonstrates how hydropower can make significant contributions to conservation efforts at regional and basin levels.
After being assessed under the Hydropower Sustainability Assessment Protocol (a predecessor tool to the Hydropower Sustainability Standard) in 2019, the project was awarded the IHA Blue Planet Prize, which recognises excellence in sustainable development.
The project has been particularly commended for its innovative use of a river offset approach, enabling hydropower development while protecting other free-flowing rivers from future impact.
Reventazón sits within a critical section of the Mesoamerican Jaguar Corridor
A hydropower project in a sensitive landscape
Located near the town of Siquirres, Reventazón diverts water from a 7km² reservoir through a tunnel to its main powerhouse, returning it several kilometres downstream. A secondary turbine ensures that an environmental flow is maintained along the bypass reach. Owned and operated by Instituto Costarricense de Electricidad (ICE), the facility forms part of a wider cascade of hydropower plants on the river.
From the outset, ICE recognised the high conservation value of the area as a crucial consideration in project planning. Field surveys began as early as 2007 to inform the Environmental and Social Impact Assessment, revealing a rich mosaic of biodiversity that included threatened mammals such as ocelots and jaguarundis, migratory and endangered bird species, amphibians, reptiles, and a number of vulnerable fish, including migratory catadromous species and even the critically endangered common sawfish.
The project also sits within the Barbilla-Destierro biological corridor, a critical section of the Mesoamerican Jaguar Corridor, and connects to key protected areas including Tortuguero National Park.
Despite the inclusion of measures to maintain river flows and protect habitats, some impacts could not be fully avoided, particularly on aquatic biodiversity. To address these residual impacts, ICE committed to a comprehensive compensation and offset strategy focused on aquatic ecosystems.
Offsetting river impacts through biodiversity conservation
One of the distinctive features of Reventazón’s biodiversity strategy is its use of a river offset. Rather than focusing solely on restoring degraded land, ICE chose to protect a nearby waterway with similar ecological functions to the impacted stretch of the Reventazón River. The Parismina River, which shares many of the same hydrological and biological characteristics, was selected as the offset site.
This offset area spans over 100 kilometres of river and is protected by an 8,178-hectare buffer zone, covering 500 metres on each riverbank. Within this zone, a wide range of conservation activities have been implemented, including revegetation of riverbanks, monitoring of water quality and flora and fauna, eco-toxicology studies, and the promotion of sustainable land use practices. Education and capacity-building initiatives are also in place to engage local communities and landowners.
The objective is not only to protect the Parismina River but to deliver a net gain in biodiversity, compensating for the species and habitats impacted by the project. Early monitoring results suggest that environmental conditions in the offset area are improving, and full implementation of the programme is expected to result in more than a 40% gain in biodiversity value.
Strengthening biological corridors and protecting wildlife
Beyond the river offset initiative, the project has made significant contributions to strengthening the Barbilla-Destierro corridor. In partnership with Costa Rica’s forest financing fund, FONAFIFO, ICE is restoring nearly 730 hectares of land, supporting natural regeneration on an additional 78 hectares, and planting more than 34,000 trees in areas that enhance connectivity around the reservoir.
During the construction phase, ICE also implemented a wildlife rescue and relocation programme. Sensitive species were carefully captured and moved to suitable habitats, resulting in the relocation of more than 38,000 animals. Early monitoring showed high survival rates among both flora and fauna.
In addition, ICE took steps to minimise construction-related impacts, such as preserving native vegetation, constructing the penstock over a bridge to protect Guayacán Creek, and relocating orchids and other epiphytes growing near work sites.
To reduce the risk of accidental harm to animals, the project team introduced wildlife protection signage and driver training for site workers. Anti-poaching campaigns and on-site awareness efforts were also implemented to discourage hunting and trapping in the project area.
At 300MW, Reventazón is Central America’s largest hydropower plant. Photo by Mario Lacayo, World Bank.
A national commitment to river protection
In 2016, the Costa Rican government formally declared the Parismina and Dos Novillos rivers as “free of barriers” and of public interest, providing long-term protection to the offset area. That same year, the Savegre and Pacuare rivers were also designated for protection from future hydropower development for 25 years. These decisions were part of a broader national strategy for basin-scale hydropower planning, which balances energy production with ecological, cultural and social values.
The approach taken at Reventazón helped demonstrate the value of such planning and supported the case for safeguarding Costa Rica’s remaining free-flowing rivers. In doing so, the project contributed not only to conservation at the local level, but to a wider shift in national policy.
Ongoing adaptation and stakeholder collaboration
Biodiversity management at Reventazón is an ongoing effort. ICE has adopted an adaptive management framework to respond to long-term environmental risks, particularly in downstream areas such as Tortuguero National Park. Monitoring programmes track river morphology, sedimentation, water quality and species populations, enabling the project team to take targeted actions when needed (for example, by stabilising eroding riverbanks with native species).
Partnerships have been critical to the project’s success. ICE has worked closely with Panthera, COMCURE, FONAFIFO, local farmers and municipal authorities to design and implement conservation activities. These collaborations have helped build trust and local ownership, ensuring that biodiversity efforts are grounded in the social and ecological realities of the region.
Insights from Reventazón’s approach to sustainable hydropower
Reventazón’s example demonstrates that with early planning, cross-sector collaboration, and a willingness to go beyond minimum requirements, large-scale hydropower projects can be developed in a way that actively supports biodiversity conservation.
By incorporating a river offset, strengthening ecological corridors, and adaptive management through continuous learning, the project highlights how infrastructure can be designed to contribute to nature-positive outcomes.
As hydropower continues to play a central role in the clean energy transition, case studies like Reventazón show that development and conservation can be designed to work in parallel – delivering energy security while protecting the ecosystems that sustain life.
Take the next step in hydropower biodiversity management
The Reventazón case study highlights how hydropower projects can integrate biodiversity considerations from the outset and deliver meaningful conservation outcomes. If you're looking to deepen your knowledge in this area, our online course on Biodiversity Management in Hydropower provides practical guidance on screening, mitigation and compliance with internationally recognised sustainability standards.
You can also read more about the Hydropower Sustainability Standard, which features biodiversity as one of its 12 ESG topics under which projects can be assessed and certified.
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